LH Interstate side cover question

Can anyone shed light on what the original purpose of the rectangular (sort of) depression in the lower rear corner of the LH side cover was for.
Mine has the depression, with no holes nor evidence of any hole repair.
Leaves me wondrin'
Cheers

Used on MK2a for a plastic 1/4 turn Dzus fastener dropped for MK3, the press tool must have too expensive to change back to pre MK2a.